This invention relates to a piston assembly for an internal combustion engine of a motor bicycle, for example.
The piston assembly for an internal engine of a motor bicycle, for example, is provided with piston bosses with which a connecting rod, so-called a con'rod, is coupled through a piston pin. The connecting rod is provided with a small end portion generally in direct contact with the end surfaces of the piston bosses to adjust or limit the position of the small end portion of the connecting rod and with a big end portion operatively coupled with a crank shaft.
In a modification, there has been proposed a piston for an internal combustion engine in which a washer or sleeve member is interposed between the small end portion of the connecting rod and the end surfaces of the piston bosses to indirectly adjust or limit the position of the small end portion of the connecting rod.
With the pistons of the described types, a deflection or swinging motion of the connecting rod is caused during the reciprocating displacement of the piston, so that the piston boss is subjected to direct or indirect, through the washer, for example, sliding and colliding friction forces by the connecting rod. Such sliding and colliding friction forces may cause the sliding and colliding abrasion or wear to the end surfaces of the piston bosses simultaneously, which may result in breakage of the engine in an adverse case.
In order to obviate the defects described above, there has been also provided a piston for an internal combustion engine in which a thin film of a chrome plating with high hardness is adhered to the end surface of the piston boss to effectively prevent the abrasion or wearing of the end surface of the piston boss. Such chrome plating is effective against the sliding or colliding abrasion or wearing, but in the conventional technique, it is necessary to carry out a finishing cutting or grinding working after the adherence of the thin film of the chrome plating. This impedes the mass production of the piston assembly.
Moreover, in the technical field for plating or coating metal powder of particles, there is known a flame coating methods, but the known flame coating method has not been utilized for coating the end surfaces of the piston bosses of the piston member of a motor bicycle, for example, of the type described above, because of the design, the dimensions, and the structure of the conventional piston member.